Oil starvation problem. I think.

[Justin Cyder]

Bit of a weird one.

For a while, my 55 Mini Cooper S has had an intermittent case of making a rasping noise on start up until the Oil pressure gauge swings around to 5 bar.

I've assumed up until now some unlucky far flung part of the engine is being starved of oil, however, I've sussed out the noise is coming from the gauge itself!

Would I be right in thinking that the oil gauge itself would work off oil pressure as they did on original minis? This is the part. Even better if anyone knows of failures on these.

[Defcon5]

I would imagine the gauge is electronically controlled by the ecu.

I used to have a Cooper S, and the speedo made a similar noise on startup

[ch427]

A pressure sensor should send the signal back to the gauge possibly via the ecu as suggested. Does the car have a warning light too?

[Justin Cyder]

Do you mean does a warning light come on? Then no. It's literally for two or three seconds when the car is started.

The oil pressure gauge is at zero and making a rasping noise whilst the engine runs & then it shoots round to 2.5 bar I.e. bang in the middle of the gauge range & goes silent. The noise is coming from the gauge itself. I guess it's just a faulty part. Looking at the diagram, it seems it's one whole part.

[ch427]

Hard to know what to suggest in this situation, i would try to get an oil pressure test done first to rule this out. You can almost be sure its the gauge at fault after that, unless you can find any evidence that there are problems with the gauges

[Mr2Mike]

They are almost certainly stepper motor driven gauges, almost all modern cars use them. Since a stepper motor gauge does not naturally zero itself when power is removed, the control electronics have to ensure the gauge is zeroed at power on by driving it until the needle physically hits a stop. At that point the gauge driver should be able to detect the gauge has "stalled" from the measured voltages of the undriven phases. However, if it can't tell for whatever reason, it will simply keep driving the gauge against the stop for the maximum possible number of steps, which will make a buzzing noise.

[Justin Cyder]

That's it then Mike - thanks for the explanation. I'd kind of assumed the gauge was driven by oil pressure direct from the engine with no real logic from me other than that's how the original mini gauge worked. It's an indivisible part according to the diagram, so I guess the solution is to replace it whole.

Thanks again.

[one eyed mick]

Learn to live with it?

[bearman68]

Be careful changing the instrument cluster - I'm pretty sure it will need coding. There's a decent chance of the car not starting if you don't code it correctly.